Taiyi divination fortune-telling

What does the "B" in Taiyi God's number plate mean?

Taiyi Shenshu, Daoism Shenshu and Liu Ren Shenshu are called the three ancient literary styles. It's good to learn one of these three styles by accident. I learned Daoism from a friend by chance, and later I wanted to learn Taiyi Shenshu and Liu Ren Shenshu, but it was difficult to learn without teaching.